Teenage Mutant Ninja Turtles: The Newest Brother
by Theboblinator
Summary: What would have happened if something else distracted the Shredder after he'd defeated the turtles before he saw Xever's fish form? Or rather, someone? And, what if this person knew April? Well for one, the turtles would get a new "brother". And for another, Donnie might just stop his attempts to get with April. (OC (Mark) x April, 2012 Version, T rated b/c of added violence.)


**Chapter 1: Friends Old and New**

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**Summary: **What would have happened if something else distracted the Shredder after he'd defeated the turtles before he saw Xever's fish form? Or rather, someone? And, what if this person knew April? Well for one, the turtles would get a new "brother". And for another, Donnie might just stop his fruitless attempts to get with April. OC (Mark) x April

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**Author's Note Part 1: You know… I ****_really_**** need to learn to stop reading stories from new categories while I'm trying to write out my own. Since the only reason I'm writing this one is because I read a crossover between this series, and Danny Phantom. Now, I'm writing out this new story where an OC meets the Turtles shortly after they meet April. There's also the fact that I'm probably going to get more hate on this story for the pairing than the story where Danny Fenton is paired with April… Why is that? I've noticed how whenever there's a crossover, people hardly complain when one character is paired with another, and yet in a story where an OC is implemented, there are a lot more complaints about who the OC is paired with. I find that extremely unfair.**

**However, there are a couple reasons for me putting this pairing in the story. 1: I simply felt like it. And 2: I've noticed that there are 0 stories that April is paired with an OC. I mean, I've seen plenty where she's paired with Donnie, or like canon is paired with Casey, but there aren't any where an OC is paired with April. And what's more, I've seen plenty stories where Casey is paired with a female OC! So, I guess that I'll be the first to write out a story that has April paired with an OC. (Note that because of this, I will mention Casey having a girlfriend, but she won't appear in the story. One OC is enough for me thank you very much.)**

**(Another Note, the Turtles, my OC, April and Casey are all 16 in this. Why? Because I'm already 17, so writing them out as if they were a year younger than me, instead of two years, is easier. That, and because it allows this to be rated T. But, don't worry. It shouldn't go past making out, if it even gets that far. After all, this ****_is_**** a children's cartoon. Though, really it's more of a 15 years old+ cartoon.)**

**But, I'm guessing that those of you who don't want to rip my head off at the moment, and have stuck around to read even after seeing the pairing, just want to get to reading the story, right? Well then, here's the first chapter of my newest story!**

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_You know, after living off the streets for a good 10 years, you would think that a sixteen year old kid would have seen everything that New York has to offer. And yet, here I am, shocked as all hell at the sight before me. Sure, at first glance it might seem like a random mugging, which is normal on the streets, or rooftop in this case, but if you looked closer, then you'd see just what it is that's surprising to me._

_The man standing there is a person well known by the people who live on the streets. The Shredder. He's known for having his own personal army, and only showed up a few weeks ago. And yet, he has connections with some of the most influential crime gangs out there. Though, I have a different reason for knowing him…_

_And then, there are the "people" that he just finished attacking. The reason I put quotation marks around "people", is because they aren't humans. Instead, lying beaten on the ground are four mutant turtles. Yeah, giant, green turtles that are outfitted as ninjas. One with two katanas and a blue mask, another with a purple mask and a bo staff, yet another with an orange mask and two nunchuks, which I already like since they're the closest weapons to what I use, and the final one with a red mask and two sais._

_As for me? Well, we'll get to me later. For now, I should probably intervene before The Shredder ends up killing the ninja turtles. You know how hero complexes are…_

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**3****rd**** Person POV:**

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Leonardo grabs the front of his shell in pain after Shredder delivers a nasty slash, before being slammed into a wall by the same man. Then, he pulls back his arm, letting the blades from his gauntlet extend, and slams them into the wall on either side of the mutant turtle's neck. Leo is shocked by this, before Shredder allows a third blade to extend and get closer to his neck with every second. "Tell me where Splinter is and I promise your demise will be swift." Shredder tells the turtle. Leo stares at the blade with wide eyes, before another voice calls out.

"Hey Tinhead!" It yells, making two combatants look in the direction it came from, only to see what looks like a miniature scythe flying towards The Shredder. Because of this, he jumps back, causing Leo to fall to the floor of the roof. The miniature scythe, which to two can now see is attached to a chain, impacts the ground between them, before a body impacts the ground, holding the other end of the chain, which is attached to another miniature scythe. Making the weapon that he's currently holding a Chain Scythe. When he looks up, the Shredder gains a look of recognition, before that recognition changes to anger.

"You!" He exclaims, extending both his wrist gauntlet's blades and aiming them at the figure. Said figure stands up, showing it to be a 16 year old male.

"Hey Shreds. So, how's the whole revenge scheme coming along?" He asks with a voice that tells the two present that he's smirking, also telling the two that he knew he'd just interfered with the scheme in question.

"I'll rip you limb from limb for your insolence." Shredder threatens in a growl. The figure places one of his scythes across his chest, as if he were holding his heart.

"Oh, you wound me so. And here I was thinking that you'd forgive and forget about our little disagreement." He says in a mocking tone, moving his right scythe so that its resting on his shoulder, while he holds the left one at his side.

"I will never forget, or forgive, those who betray me." Shredder says with narrowed eyes, making Leo look between the two with surprise.

_This guy… _betrayed_ The Shredder?_ He asks himself in shock, surprised that anyone would dare to do so, after the stories that Master Splinter had told him and his brothers about the man who'd just defeated them.

"Aw, that's too bad. Cause I was really hoping that I wouldn't have to fight you… Then again, maybe I won't." He says, gesturing to something behind Shredder with his left scythe, just as the sound of someone, or rather some_thing_, can be heard gasping for breath.

"What?" Shredder asks, looking in the direction of the gasp to see a mutant fish-man lying in a puddle of mutagen. While The Shredder is distracted, the mystery guy runs over to Leo, and lays one of the turtle's arms over his neck, helping him to stand. He helps the turtle over to his brother's, who are also pushing themselves to their feet.

"Come on. Knowing him, he'll only be distracted for a few more seconds." He grunts out, getting quick nods from the turtles, who then leap down into the alleyway below, and then enter the sewers. However, that doesn't stop them from hearing Shredder's cry of anger. They all let out a breath of relief, before Leo is able to stand on his own. Almost as soon as this happens, the mystery guy is pressed against the side of the tunnel, with one of Raph's Sais at his throat.

"Alright you, just who are you, and how do you know The Shredder?" He asks with a glare, before Mikey speaks up.

"And how is it that you can mock him?" He asks in a breathless voice, getting a slap to the back of the head from Donnie. "Ow!" He exclaims, making Donnie and Leo shake their heads in exasperation, before Leo walks over to Raph and places a hand on his shoulder.

"Come on Raph, this guy just helped me." He says, making the red masked turtle turn his glare to his brother.

"Yeah, and what if that's just a way to gain our trust?! I mean, he _knows_ The Shredder!" He exclaims, gesturing to the guy, before the two are interrupted by the guy in question, who gives a cough into his closed fist.

"You know, as _great_ as it is seeing the four of you bicker amongst one another, don't you think that you should all get looked at?" He asks, gesturing to their injuries, which brings the four turtle's attentions back to them. They all wince at the pain, but continue to look at him.

"We will, but Raph does bring up a good point. How _do_ you know The Shredder?" Leo asks.

"And how can you- Ow!" Mikey exclaims, placing his "hands" on his head after Donnie smacks him again. The rest roll their eyes, including the mystery man, before they look at him.

"Alright fine. I'll give you the simplified version." He says, before casting a glance at Mikey. "_Really_ simplified." He says, making the others share smirks despite themselves. "Me, try to steal from Shreds. Me get caught. Him make me apprentice when he sees potential. Me figure out him evil. Me escape. Me on run from Foot. Me see attack. Me help you. Now, we here." He tells them, adding hand motions as he looks at Mikey, making Raph's smirk widen. A little voice in the back of the violent turtle's head says that he already likes the new guy.

"Wait, so, you were taught by The Shredder, and then _ran away_? But, how?" Donnie asks. "I mean, I'm pretty sure you would have been caught by his Foot soldiers." He continues, making the guy turn to look at him.

"Hey, I only just ran away a couple days ago. But I'll tell you this much, they've been on my tail ever since. Hardly get any sleep at night." The guy says, rubbing his face to get the point across. "Anyways, I've told you what happened. Now, don't you think it's about time you four got some kind of medical attention?" He asks them, his voice telling them that he actually cares for their health, and making them wince again when they remember their injuries.

"He's right guys. Let's get back to the Lair." Leo says, getting nods in response. However, Raph turns to look at the guy.

"But if you try anything funny…" He trails off, holding one of his Sai's up for emphasis. The guy holds up his hands, free of his Chain Scythes since they were at his waist now, in surrender.

"No problem. But I mean, do you _really_ think that I'd help you guys just to kill you off?" He asks them.

"Guy's got a point." Mikey agrees, making the other three send mild glares his way. Well, Raph gives him a full glare, making his shrink back. "Just saying!" He exclaims, making them sigh in exasperation.

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The group of five walk towards the lair, the four turtles surrounding their new "guest" as they do so. The figure mentally rolls his eyes at this. _These four are already injured. If they think they'd be able to take me on in their situation, then they're sorely mistaken._ He thinks as they near the turnstiles that mark the beginning of their Lair. As this happens, Raph turns to glare at him again. "I'm warning you… One wrong move…" He trails off, making the figure roll his eyes visibly this time.

"Yeah, yeah I get it. You'll flay me alive." He remarks sarcastically, making Raph steam slightly. However, none of them were expecting what would happen when they walked into the Lair.

"Hey guys!" A female voice calls out, making the figure stiffen slightly. "I was wondering when- Oh my God! What happened?!" She calls out, getting groans from the turtles in response.

"We got into a fight with Xever and Bradford." Donnie says as they make their way to the main area, and slouch in different areas.

"Yeah, and then The Shredder turned up." Mikey adds, making the girl gasp and cover her mouth with her hands. **(I don't think I need to describe teenage April's appearance.)**

"Are you guys Okay?" She asks them with concern present in her voice.

"Who me- I mean! Us? Yeah, yeah, we're fine." Donnie replies, stuttering over the beginning.

"Yeah, turns out we got a little help." Leo adds, making Raph scoff slightly.

"Like we needed any." He says, unwilling to accept the fact that they needed help.

"Really? Who-" She's cut off by the guy in question.

"April?" He asks, bringing all attention to him, and giving the turtle's their first good look at him since he'd been shrouded in shadows since they first saw him. He was wearing black combat boots, and yet they didn't make any noise when he walked around, meaning that he'd tampered with them to make it so they were silent. They partially covered the loose fitting black pants that he wore, which were held up by a brown belt, containing pouches on the side for other small ninja equipment. Tucked into the pants was a dark blue, long sleeved T-shirt. Situated just below his shoulders, on his forearms and the tops of his hands were metal armor pieces that would protect him from any weapons that other ninja may use against him. Tucked into the top of the shirt was a mask that would only cover from the top of his nose down. He had bright cobalt eyes, and rich black hair. Tied around his neck was a white scarf that reached down to the back of his waist. **(For inspiration on outfit, look in my Bio.)**

Both of his scythes rested on the right side of his waist, with the chain between them hanging down to just above his knee, some of it no doubt tucked into one of the few pouches on his belt. Said scythes were identical to the ones that Tsubaki could become in the anime "Soul Eater", with the difference being the color scheme. In place of the yellow handles, they were instead black. And the yellow dots on the metal were instead cobalt in color. Said metal was changed as well, being a duller grey.

"I'm sorry, do I know you?" April asks with a raised eyebrow, which actually gets a laugh from the teen.

"Yeah… Yeah, you do." He says, removing his mask, which shows that he's smiling. "It's me… Mark Daniels." He tells her. At the announcement, April's hands fly up to her mouth as her eyes widen, before she lowers them slightly.

"Mark?" She breaths out, getting a small chuckle from the teen in question.

"Yup, in the flesh." He replies, holding out his arms to prove the point further. However, he's just as surprised as the rest when April suddenly rushes forwards and wraps him in a hug. The turtles are more surprised when after he gets over his own surprise, Mark hugs her back. And… Donnie's just a _little_ jealous. "Sorry about not keeping in touch." He apparently apologizes when April eventually pulls away, scratching the back of his head sheepishly.

"I haven't heard from you in _weeks_! I thought… I thought that you'd been taken." April says, whispering at the end. Mark flinches at that, but before he can reply, Raph cuts in as the turtles stand up and walk over to stand in front of them.

"Whoa, whoa, hold on a minute. April, you know this guy?!" He asks, Donnie popping up at his side a second later.

"And well enough to give him a hug?!" He asks, before shrinking back when the group's eyes turn to him.

"Yeah. Guys, meet Mark Daniels. He's my best friend." She says, and none of the turtles miss the slight frown that Mark shows at the words "best friend", before it disappears. "I've known him since elementary school." She continues, oblivious to what the turtles had seen. And Mark doesn't show what he'd done either.

"Yeah, the first time you ran into me, you thought I was gonna take your money." He chuckles, getting a slight blush from his friend in response.

"Well it's not my fault that the first time I met you was when I was taking a shortcut through an alleyway." She complains, getting louder laughter from Mark, and unknowingly letting the master of the Lair know of his presence.

"No, but you can't blame me for being a street rat either!" He exclaims, before another voice interjects in the conversation.

"Well, you do not look like much of a "rat" to me." Everyone turns to look at the new arrival, and see Master Splinter standing there with his jade**(?)** staff. "In fact, you look very much human." He continues, the turtles bowing at his presence. Meanwhile, Mark looks slightly to the side while rubbing the back of his head.

"Four walking, talking ninja turtles, and now a walking, talking, possibly ninja rat. Huh, now I've seen it all." He mutters, before looking back at Splinter. "Sorry, didn't mean any offense by my phrasing. It's just what people like me are called." He tells Splinter, not that phased by what he's seeing after what he'd seen earlier, though still surprised. At his words, Splinter hums, and strokes his beard.

"You are not surprised. Why?" He asks, making Mark raise an eyebrow.

"With all due respect sir, I've just seen four walking, talking ninja turtles fight down my previous, insane, egotistical master and live to tell the tale. I'm honestly still trying to get past that." He says with a shrug, making Splinter's eyes widen.

"You were The Shredder's apprentice?" He asks in shock, before the first part catches up with him. "And my sons faced him?!" He continues, turning to face the turtles in question.

"Uh, yeah. Though, like I said, previous master. I kinda found out he was evil and left." Mark says with a shrug, though, it seemed that fate wasn't done going over this part of his life with him.

"Why would you want to learn from The Shredder?!" April asks him, making him drop his head into his hands with a groan.

"I already told you. I escaped when I found out he was evil. Meaning, I didn't know until that point. The only thing that he would let me do was practice with the Foot soldiers in my room, and the training room attached to it. I only found out about him being evil when I snuck out of it one day, and heard him talking about four "insolent worms" interfering with his plans with Chris Bradford. Then, he goes on to talk about the local gangs, and how he was working with them. I put two and two together, and ran away." He tells them.

"So you didn't think it was suspicious that he confined you to your room for a few weeks to train?" Donnie asks, trying to find flaws in the person in front of him, since he didn't like how close he was to April. As smart as he was, he lacked tact, and thus, did not realize that in trying to do this, he could possibly end up breaking Mark's friendship with April if he brought up a major flaw. Though, luckily, the chances of that happening were slim to none.

"Hey! I thought that was the guy's training method! Excuse me for not knowing a lot about a guy who only showed up the day before I met him." He says, his tone changing to sarcasm near the end, making Donnie give a slight glare of annoyance. "But, as _fascinating_ as I'm sure this is for all of you, don't you have wounds that need to be taken care of?" He asks, gesturing to the four of them for emphasis. The all wince once again, before groaning in annoyance at being reminded, and slump onto the nearest resting place they could find that wasn't the ground. Well, Raph sits on the ground and leans against the arcade game.

"You were all _very_ lucky." Splinter tells them all, getting a nod in agreement from Mark. However, Raph looks up at Splinter at this from his place leaning against their arcade game.

"I think we define that word differently Sensei." He says, making Mark speak up.

"Didn't you hear what I said earlier? You guys _lived_ after facing good-ol' Shreds. Not many can claim the same." He says, getting a nod from Splinter.

"Mark is correct. Few have _ever_ faced The Shredder and survived… And how do you work up the courage to mock him?" He asks Mark absentmindedly, getting a groan out of the teen in response.

"He was just so fast." Mikey speaks up from his place lying on a pile of boxes.

"It was like he was _everywhere_ at once." Donnie agrees from his place sitting on one of the sofas in the center of the room.

"You were right, about us being overconfident Sensei." Leo speaks up from his place leaning against the wall next to Splinter. "There are some things, we're just not ready for." He tells Splinter, who places his hand on Leo's shoulder.

"Perhaps." He agrees. "But that no longer matters. It is clear now that The Shredder is a problem that will not go away." He continues, looking over at the others, who look up to meet his eyes. "So prepare yourselves my sons… Because as of this moment… We, are, at, war." He says, narrowing his eyes.

"Well then, I'm guessing you could use all the help you could get." Mark speaks up, bringing attention back to him as he walks over to stand in front of Splinter. "I'd like to offer my own help, if you'll allow me." He says, getting onto his knees and bowing in front of the rat, making the others eyes widen.

"Mark, what are you talking about?" April asks.

"I'm saying that I'd like to help take down my former master. I want to help protect the city. I want to help your friends… And I want to help you." He tells her. Splinter hums at this, stroking his beard in thought as he stares down at the teen kneeling before him.

"This is a difficult decision…" He says, walking towards the sliding door that leads to the dojo part of the Lair. "I will have to meditate on it." He announces, closing the door behind him. Not five seconds later, it opens back up to show Splinter with a small smirk on his face. "You may." He says, before closing the door again. At this, Mark looks up in surprise, before a smile works its way onto his face.

"Thank you… Sensei." He thanks Splinter, before standing up and facing his new friends. "Well… Think you guys have room for one more?" He asks them, getting small smiles out of Leo and Mikey, a full blown grin from April, a small smirk from Raph, and a _very_ tiny frown from Donnie. Though, we all know why _that_ is.

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We can see Mark sitting in one of the sofas in the middle of the main room in the lair with April sitting next to him, a notebook opened in front of him while the turtles are in varying positions around him. Raph is playing on the arcade game, Donnie is off in his small lab space, Leo is sitting near Mark looking at the television as it plays an episode of Space Heroes, and Mikey is balancing on his skateboard. All four of them are wrapped in bandages from their fight with The Shredder, and they occasionally flinch from a slight bit of pain.

_Dear Journal,_

The top of the notebook's page reads, getting a small giggle from April. "Journal, really?" She asks, getting a small glare from Mark, though some humor glints at the edges.

"Hey, I'm a guy. Guy's don't have diaries, we have journals." He tells her, getting another giggle from her.

"Sure." She pretends to agree, making Mark give off indistinguishable grumbles as he turns his attention back to his "journal", unaware that Donnie is doing the same, but for a completely different reason.

_Today did not go how I expected. Sure, it started out with running from Foot soldiers, which was then followed by running from Foot soldiers, and then some more running from Foot soldiers._

As he writes this out, April punches him good naturedly in the arm. "Get enough exercise?" She asks rhetorically. Making him turn to grin at her slightly.

"Hey, I'm quite the free runner now thank you very much. Running for your life can do that to you." He says, turning back to look at his journal.

_But the real surprise was when I ended up seeing my previous master, the guy who sent them all after me, attacking a group of four mutant ninja turtles. Needless to say, I jumped in before he could kill Leo, the one who uses katanas. We got into a slight argument, before he was distracted by one of his lackeys, allowing me to help Leo and his brothers escape into the sewers._

April reads over his shoulder as he writes this, and gives a small laugh. "Lackey?" She asks, making Mark turn to give her another smile.

"Hey, can you think of anything else that guy might be to Shreds?" He asks, getting a chuckle out of April as she shakes her head. "Didn't think so." Mark agrees as he turns back to writing in his journal.

_After returning to their home, I met up with my-_

Mark pauses for a second here, which April happens to notice slightly before he continues.

_-best friend April O'Neil. Then, I met the "father" of the turtles, and ended up joining his mish-mashed family in order to help take down Shreds. However, not everything is good. I found out that April's father got kidnapped (or maybe father-napped) by these weird alien robots with brain aliens in their chests. Though, after having them explained to me, not by Mikey, I found out the aliens are actually situated in the abdomen area of the robot, not the chest. They're called the Kraang, and their apparently stealing New York's scientists to change this goo substance that they brought from their dimension._

_Turns out that goo is called Mutagen, and it's the reason that Shredder's lackey changed into that fish-man thing back on the roof that he fought the turtles on. I can only hope that I don't get hit by any of it. And if I did, I can only hope that it changed me in a different way than it did fishface._

After righting this he pauses, and turns to face April. "Say, has anyone been hit by the Mutagen and _not_ changed into some freak of nature… Present company excluded." He says, referring to the turtles and Splinter. April thinks about it for a second, before looking back at him.

"You know, there was this one scientist that gained psychological abilities from it." She tells him, making him tap the pen he was using to write on his chin.

"Hmm… Wonder if I could get something similar to using the Force if I got covered in mutagen… Ah, wishful thinking." Mark says, before going back to his journal.

_But, that's about it for today. I'm excited about my new life, and look forwards to spending it with my friends. Both old and new. –Mark Daniels_

He finishes writing and lays the notepad on his lap, before leaning back in the sofa as April pats him on the shoulder with a smile, before getting up and making her way over to Donnie with a slight eye roll when he calls for her. As she does this, Mark watches to make sure she's gone, before he picks up his journal, and adds some more at the bottom.

_P.s. Still haven't worked up the courage to tell April just how I feel about her. And now, it seems that I may have to worry about one of my new friends, Donnie, who appears to have feelings for her as well… I'd rather not have this happen. I mean, as great as it would be for him, he's a turtle. I just… I don't know. At the current moment, I can't see it happening. And if I'm honest, I really _don't_ want it happening. But, this just means that I'm gonna have to tell her sooner rather than later, or risk losing her to someone else… If I haven't already during the weeks I spent as Shredder's pupil. Great, that's not really the best thought to have…_

Mark sighs as he finally closes the notebook, and leans back in the sofa once again. When he's comfortable, he looks around to see Leo staring at him. At this, he looks down at his notebook, before looking back at Leo, only to see the katana wielding turtle looking at the television once again. _Man, I'm gonna need to find a _really _good hiding place for this thing. The _last_ thing that I need is for any of these guys to find it. Least of all either Donnie, or worse, April._ He thinks to himself, before shaking his head and turning to watch Space Heroes with Leo. _But despite that… I feel like life here is going to be a good one._ He thinks as a small smile makes its way onto his face.

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**Author's Note Part 2: Well guys, here's the first chapter. Not sure if I'm gonna post it tomorrow or not (seeing as it's pretty late tonight) but if I do, then I'm either going to work on one more chapter and then get back to updating my other stories, or I'm only gonna post this one chapter, and then work on my past stories. But whatever choice I make, I should be back to updating my other stories soon.**

**(Sorry about the long hiatus on all my stories, but I've not only been working on this one, but another two that I've recently started, and two others that I haven't even posted on the site yet, but started a while ago.)**

**Now, for those of you who stuck around this long, I'd like to thank you all, and hope that I can keep you all entertained with the chapters to come. Thanks for taking the time out of your day to read this, and I hope to see you next time!**


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